1. Field of the Invention
The invention relates to a slab-shaped building element, particularly to a wall element of storey height, of light weight concrete reinforced by reinforcing rods.
The reinforcement of building elements of light weight concrete is determined for transport and assembly and may, if suitably dimensioned, provide the further possibility of using such elements as loadbearing building elements.
2. Description of the Prior Art
A load-bearing building element of this kind has, for example, been described in the Austrian Pat. No. 355,271. Such an element is preferably made by using expanded additives, such as polystyrene, expanded clay or the like, and has vertically continuous channels adapted to receive reinforcable in-situ concrete as well as substantially horizontally arranged reinforcing rods terminating at the two vertical side faces in grooves extending over the full height of the element. The grooves of adjacent building elements form together a hollow space which may be filled with in-situ concrete and vertically reinforced.
The weight of such wall elements is substantially lower than the weight of wall elements of heavy concrete and may, hence, constitute complete walls and be put up on the site without great difficulties. Wall elements of lightweight concrete have the further advantage that they provide good heat-insulation and the possibility of prefabricating them with very smooth surfaces so that further treatment will be reduced to a minimum. The described advantages outweigh the higher costs in comparison with wall elements of reinforced concrete.
Difficulties arise from the fact that the bond between the lightweight concrete and the reinforcing rods is not such as known from heavy concrete as the extent of shrinkage after the drying and hardening of the lightweight concrete exceeds the shrinkage of the heavy concrete by a multiple, and the sliding resistance of the reinforcing rods is substantially reduced because of the substantially lower density of the lightweight concrete. The shrinking lightweight concrete, therefore, peels from the reinforcing rods, whereupon the rods become susceptible to rust because of the air which can now enter into the hollow spaces, and the bonding effect is destroyed.
It has further been tried to produce so-called multi-layer building elements comprising an intermediate layer of lightweight concrete arranged between two layers of heavy concrete reinforced by two vertical reinforcing rods or wires which may be prestressed, if required (German Pat. No. 803,943). The heavy concrete portion of such elements is relatively great so that the reduction in weight and heat-insulation is lower than with wall elements exclusively made of lightweight concrete.
As described in German Pat. No. 192,927, moulded parts of clay or the like are reinforced by iron inserts disposed in the hollow space of the moulded part. The hollow space is then filled with a hardening material, such as cement, ensuring the bonding effect between the moulded part and the iron insert.